Computer Simulation of Morphologies and Optical Properties of Filled Diblock Copolymers

Abstract

We integrate two computational techniques in order to determine the optical properties of self-assembled mixtures of diblock copolymers and nanoparticles. To determine the morphology of the system, we first use an approach that combines a self-consistent-field theory (SCFT) for the diblocks with a density functional theory (DFT) for the particles. Using this SCF/DFT model, we focus on the lamellar phase of AB diblocks and calculate volume fraction profiles for systems containing selective or nonselective nanoparticles. We use the volume fraction profiles from the SCF/DFT and assign typical dielectric constants for the different polymer domains and the particles to characterize the dielectric properties of the composite. A finite difference time domain (FDTD) technique is then used to simulate the propagation of light through this heterogeneous material. The results of this study allow us to determine how the polymer-particle interactions affect the spatial distribution of fillers within the polymer matrix and how this distribution in turn affects the optical properties of the nanocomposite. The findings can provide guidelines for facilitating the design of photonic band gap materials.

Block copolymer–nanoparticle composites: Structure, functional properties, and processing

“…Nanoparticle shape: BCP composites containing anisotropic NPs may exhibit improved mechanical, optical, electrical, and photovoltaic properties compared to BCP composites containing spherical NPs [134][135][136][137]. The incorporation of anisotropic NPs is more challenging than that of spherical NPs because the former is associated with an additional entropy of particle orientation [138].…”

“…Ordered block copolymer nanostructures can possess interesting optical characteristics due to their periodic nature and the optical contrast between different polymeric domains [41,230] that can be further modulated by selective incorporation of NPs into a particular polymeric domain that can control optical properties of the composite materials such as reflectivity [136]. For example, incorporation of 2 vol% (10 wt%) PS-modified gold NPs (diameter = 2.5 nm) into lamellar polystyrene-poly(ethylene/propylene) PS-PEP BCPs increased reflectivity from ~80%…”

“…13) from ~560 nm to ~640 nm [232]. A combination of self-consistent mean field and density functional theories showed that the optical properties of BCP-NP composites depend on the type and distribution of NPs [136]. The incorporation of NPs into a polymeric domain of diblock copolymer can increase the domain characteristic size and modify the refractive index, resulting in modulation of the optical properties [136].…”

“…A combination of self-consistent mean field and density functional theories showed that the optical properties of BCP-NP composites depend on the type and distribution of NPs [136]. The incorporation of NPs into a polymeric domain of diblock copolymer can increase the domain characteristic size and modify the refractive index, resulting in modulation of the optical properties [136]. For polymer composites containing randomly distributed NPs where the NP size is smaller than the wavelength of the light, the optical properties can be estimated from the volumetric average of the components of the composite [62].…”

A Strategy to Decorate the Surface of NPs and Control their Locations within Block Copolymer Templates

“…Since NPs such as Au, Ag have different colors with varied sizes, polymer-inorganic NPs can produce certain colors.The simulation results by Balazs group showed that the polymer-particle interactions affected the spatial distribution within the polyme matrix and their optical properties changed according to the particle distribution (Buxton et al, 2003). When the particles are added, band gaps are more defined with 100 % reflectance with wider frequency gap.…”